The invention relates to a punch device for electric sheets, in particular, for punching rotor sheets or stator sheets for electrical machines.
In the production of electric sheets, in particular metal sheets for electrical machines, various fabrication processes can be used to provide these sheets with stator notches or grooves, rotor notches or grooves, ventilation holes or other cutouts. To achieve this, frequently so-called notching presses are used for single-notch processes, in which notches or grooves are produced individually, one after the other. This method combines cost-effectiveness with high flexibility when different punch radii and a large variety of hole patterns are to be produced. Loading and unloading the notching press is done either manually or automatically.
An example of a notching press has been disclosed by document DE 101 07 484 A1. This reference discloses a mechanical ram drive that allows the adjustment of the pivot axis of a force-transmitting lever via an eccentric. A servo motor is used for the adjustment of this eccentric. Thus, the press stroke of the punch device can be adjusted during operation.
Referring to this solution, the maximum applicable force is a function of the position of the eccentric because said eccentric changes the effective length of the lever arms of the pivot lever, depending on the position of rotation. If an eccentric with minimal eccentricity is used, the degree of stroke adjustment is likewise minimal.
Document EP 0364715 also discloses a notching press system with a mechanical ram drive. Again, an eccentric is used to adjust the stroke length, said eccentric being adjusted via a pneumatic cylinder. The adjustment of the stamp stroke is fixed by the end positions of the drive cylinder.
Considering this, the object of the invention is to provide an improved device for the automatic punching of electric sheets.